heavy thighs

Just wondering does anyone else get a heavy feeling in their thighs from using opiates? I often do, not every day but often. Sometimes it`s quite painful but otherwise just a dull thud. Still I`d rather it than the actual pain. I have two aunts who have chronic pain in different areas from me but we all have the same symptom of heavy legs. I`m not sure if this is a symptom of the opiates or the pain condition itself so I`m curious.